1. Field of the Invention
The present invention relates to a method for manufacturing a nonlinear optical thin film, and more particularly to a method for manufacturing a nonlinear optical thin film using silica glass.
2. Description of the Related Art
Various kinds of nonlinear optical materials with a light control function have been proposed for applications to optoelectronics. Among those nonlinear optical materials, LiNbO3 (lithium niobate) is a typical example in widespread practical use.
In the case of lithium niobate, however, when used in optical elements, loss arises caused by differences in physical properties, such as refractive index or thermal expansion coefficient, between lithium niobate and glass as a connection member. Therefore, there have been requirements for nonlinear optical materials based on silica glass toreplace lithiumniobate. Such a silica-glass-based nonlinear optical material is disclosed in Japanese Patent Laid-Open Publication No.6-340444, for example.
However, those nonlinear optical materials based on silica glass do not necessarily have sufficient optical characteristics, so that their characteristics need to be improved further for practical use.
The present invention has been made to solve the above problem and has as its object to provide a method for manufacturing a silica-glass-based nonlinear optical thin film having sufficient nonlinear optical characteristics.
To achieve the above object, according to the present invention, there is provided a method for manufacturing a nonlinear optical thin film, comprising forming a thin film of SiO2xe2x80x94GeO2 system on a substrate by electron beam evaporation while performing ion beam assist and performing poling by applying an electric field to the thin film.
According to an aspect of the invention, the method for manufacturing a nonlinear optical thin film uses any of argon, helium and neon ions for ion-beam assist.
According to another aspect of the invention, the method for manufacturing a nonlinear optical thin film performs poling by applying an electric field simultaneously with electron beam evaporation.
According to an additional aspect of the invention, the method for manufacturing a nonlinear optical thin film uses a target deficient in oxygen in electron beam evaporation.
According to yet another aspect of the invention, the method for manufacturing a nonlinear optical thin film comprises forming a thin film of SiO2xe2x80x94GeO2 system on a substrate by electron beam evaporation while performing ion beam assist and orientation including ion beam assist at lower energy than that in the thin film forming step, wherein the ion-beam radiation facilitates orientation.